looking for STL codec advice

[richard.vanderveen]

It seems I need to build an STL over the big bad internet ;D
I know a lot of you guys use the Barix boxes, but I really don't wanna use MP3 and I thinl Lineair is looking for trouble over the WWW. APT offers the Silver stream in/stream out, Comrex offers the BRICLink and I can get 2 APT Worldcast Horizon IP Codecs for a very decent price.

Price is definately an issue but so is the earlier mentioned reliability. If we end up with the Comrex, something else in the total setup needs to go... The APT surestream technology appeals to me, but I have no experience whatsoever with the APT Silver line so I would like to hear from someone that has. I know the Comrex BRICLink is pretty much rock-solid, but is it really 50% better (it is 50% more expensive) than the APT? Is FLAC really an option over the WWW?

Last: would the Worldcast Horizon setup be a possible solution?

 

[stephend2]

anything over the www, use the comrex. I suspect the apt units are good as well but I have not personally used them. Barix can run mp3 well, if you're doing pcm, connection needs to be near perfect. I did some work with a station that was running PCM over the internet to their transmitter site, the only reason it worked well is because we knew the network end to end, they were in the same building with their ISP at the studio, I was providing them with connectivity from my wireless isp that is quite stable, there was plenty of bandwidth available. I would not try it on a cable connection ever, DSL only if you can verify that the connection to the modem is perfect, if you're close to the end of the line, there will be errors and it will cause you trouble.

I can't speak for the apt silver units specifically but the higher end codecs such as comrex and I'm sure tieline does this as well, have dynamic buffer management that is very good at dealing with varying connection conditions. I would have a hard time trusting something less such as barix to a mission critical task unless I had complete end to end control of the network, in my case i'm using barix instreamer and exstreamer 100 to feed an AM station that I have a p2p wireless shot to that I control. I've since put some internet traffic on that same link as I've colocated an access point on our wireless network on the tower, in that case I have placed a router at the site with some QoS that guarantees the station's barix its bandwidth regardless of any other traffic on the link, seems to work well.

 

[chriscollins]

Comrex... It is the best way.

 

[oldiesstation]

The more cost effective Silver I/0 would be a great choice as well. You mentioned cost as a factor.Units offer surestream and they finally manned up and went with balanced xlr's instead of RCA's.Keep in mind APT wrote the book on coding technology.

 

[rew]

I have been using the Horizon units for almost 2 years now. I used them on a DSL line and it worked good. the only problem now and then the DSL would go crazy. Now I am using these same units over a 5.8 Ghz unlicensed link and its working great. I still have the DSL but it is connected to a Barix box that is used as a backup. The Horizon units work good for me but it all depends on your connection. You can set the buffer time from a few ms to several seconds. This delay will mess with some people who try to listen to air while they talk. I would think this would be the same on all IP codec devices.

 

[xmusicmatt]

Don't forget the Telos Z/IP ONE

http://telos-systems.com/zip-one/

 

[oldiesstation]

He mentioned price as an issue. you can get a pair of Silvers for less that 1 zip one,nothing against it at all.guessing a pair of those would run 3k plus.

 

[RolfTaylor]

I have no experience with sure stream, but I can say that the good results using the APT-X algorithm are due to the fact it is sample based rather than frame based. This means you can use small packets and therefore you can reduce, or eliminate, the audibility of drop outs. This technique is a simple form of error concealment.

I helped many customers tweak their APT codecs with results much better than I would have predicted.

Rolf Taylor

He mentioned price as an issue. you can get a pair of Silvers for less that 1 zip one,nothing against it at all.guessing a pair of those would run 3k plus.

 

[comrex]

Consider me biased but I'd like to add a thought
Reading the APT-x White Paper in the latest issue of Radio World Engineering Extra, it seems that "SureStream" is a marketing name for creating a redundant stream. Obviously, this will have an advantage if you're blessed with a redundant network to run it on, but I don't agree that it's the most effective technique for adding resiliency to a single network connection (as the APT-X folks seem to imply).
Some other competitors tout FEC, which can be effective for short packet errors, but requires that long delays be implemented to cover longer burst errors. From the Comrex corner we've implemented an intelligent algorithm based on ack-less retransmission on request and subject to current playout buffer. This balances network utilization and delay, and is a better approach in my view since about the worst thing you want to do to a network that's suffering congestion is to attempt to cram a lot more data into it.
Guaranteed service over un-guaranteed networks is tricky business however you slice it. Besides soliciting happy user reports, my best advice is to take advantage of the liberal demo offerings available through the various manufacturers and "kick the tires" so to speak.
Best
Tom Hartnett
Technical Director
Comrex

 

[stephend2]

I will confirm that comrex really does know what they are doing when it comes to IP audio and making it as resilient to varying network conditions as it can be.

 

[richard.vanderveen]

Consider me biased but I'd like to add a thought

;D This is exactly the issue I am dealing with... As far as I'm concerned Barix is off the shortlist. I have read pretty good 'stories' though about the APT Silver series, and I seriously doubt (forgive me...) if the 50% extra cost compared to the BRICLink is worth it. The extra cost will need to come out of the budget of the rest of the project. So I'm looking for a good balance between cost and reliability (but hey, aren't we all...).

I hope you will be at IBC?

 

[chriscollins]

It seems I need to build an STL over the big bad internet ;D
I know a lot of you guys use the Barix boxes, but I really don't wanna use MP3 and I thinl Lineair is looking for trouble over the WWW. APT offers the Silver stream in/stream out, Comrex offers the BRICLink and I can get 2 APT Worldcast Horizon IP Codecs for a very decent price.

Price is definately an issue but so is the earlier mentioned reliability. If we end up with the Comrex, something else in the total setup needs to go... The APT surestream technology appeals to me, but I have no experience whatsoever with the APT Silver line so I would like to hear from someone that has. I know the Comrex BRICLink is pretty much rock-solid, but is it really 50% better (it is 50% more expensive) than the APT? Is FLAC really an option over the WWW?

Last: would the Worldcast Horizon setup be a possible solution?

I did FLAC 15K over my Comrex on the WWW... I recommend that preset as opposed to the full spectrum FLAC. It drops your bits down to around a 700k stream.

We had some hiccups with the regular FLAC... Not too many, but enough to make a change. There is a station here in town that uses our STL tower to get to the TX... They have Comcast business class Internet at their place. It can barely do AAC without breaking up.

It's difficult to use the linear options if you don't really have a lot of control over the path. We pulled it off, and Stephen mentioned it earlier. My network infrastructure is unique and uncommon for most places. I gave the box a Static IP on the Web with 10 Meg bidirectional allocated *only* to it. I still had 'bumps' until I did the FLAC 15K preset.

 

[RolfTaylor]

To play devils advocate here, let me say that the original concept for sure stream was that you would use 2, 3, or more separate networks. The real question in my mind vis-a-vis this concept for USA was that DSL here is not all that cheap so that the price of 2 or 3 DSLS with sufficient bandwidth is not really cheaper than just getting a point to point T1 which is regulated and has to perform.

And the really low budget operations will not tolerate the cost of more than one DSL line.

If you are using an APT codec on a single network Sure Stream should be turned off and you should compare APT-X with the other algorithms in the box (despite being only 4:! you will probably find APT-X (suitably tweaked with regards to packet size and buffer size).

My experience a couple of years ago was that the low delay (therefore allowing more buffering for a given total delay) and error concealment properties make APT-X surprisingly competitive wth the far more sophisticated approaches offered by Comrex and Telos. To be fair, Comrex was the first with such an approach. To my knowlege no-one other than Telos has anything nearly as smart/clever as Comrex.

Rolf Taylor
(Formerly with both Telos and then APT)

Consider me biased but I'd like to add a thought
Reading the APT-x White Paper in the latest issue of Radio World Engineering Extra, it seems that "SureStream" is a marketing name for creating a redundant stream. <SNIP>
Best
Tom Hartnett
Technical Director
Comrex

 

[stephend2]

I'll say the FLAC worked good on that one, as does the barix doing PCM now. Not bad for the last leg being a 15 mile wireless shot.

 

[Grounded Grid]

Consider me biased but I'd like to add a thought

;D This is exactly the issue I am dealing with... As far as I'm concerned Barix is off the shortlist.

That's a shame. I have a network of 30 Barix units, handling everything from studio feeds, network audio, EAS receiver links and transmitter program feeds, all done over the internet. The performance of the Barix boxes is excellent and they're saving the owner some $3,500 per month over the dedicated, yet increasingly unreliable DS0 lines from the phone company that they used to use. In one case, an owner elected to feed two co-located AMs from a single Barix link... one transmitter on each side of the stereo channel.

The real trick is in how you set them up. If you're lucky enough to have your units within the same phone company, you can use DSL on both ends and stay within the company's network. Even then, I have channels that use cable with good results..

To be fair, I also have a pair of Bric-Links on an FM. They're on a fiber link, so bandwidth isn't an issue for the PCM setting I use. The Bric-Links have performed well in that application.

 

[richard.vanderveen]

As far as I'm concerned Barix is off the shortlist.

That's a shame. I have a network of 30 Barix units, handling everything from studio feeds, network audio, EAS receiver links and transmitter program feeds, all done over the internet. The performance of the Barix boxes is excellent...

Unfortunately they don't offer AAC or FLAC and I don't want to go MP2 or MP3...

If you are using an APT codec on a single network Sure Stream should be turned off and you should compare APT-X with the other algorithms in the box (despite being only 4:! you will probably find APT-X (suitably tweaked with regards to packet size and buffer size). My experience a couple of years ago was that the low delay (therefore allowing more buffering for a given total delay) and error concealment properties make APT-X surprisingly competitive wth the far more sophisticated approaches offered by Comrex and Telos.

You are saying the Worldcast Horizons are a liable alternative too?

 

[comrex]

Richard,
I will indeed be at IBC Fri and Sat in and around the Vortex UK stand. I hear you that the BRIC-Link is more expensive than the APT Silver. You are getting balanced pro level analog, AES3, duplex operation, FLAC, and the AAC suite over the low end Silver, so I don't think it's a bad value.

Tom Hartnett
Technical Director
Comrex

 

[gtomas]

You definitely DO NOT want to use something simple as Barix, as these units have no intelligence built what-so-ever and will just send out the stream and the receiver just waits for the stream and you are the sole mercy or unreliable Internet whether the packets actually arrive or not. You really want some of the codecs specifically built for connections over the uncertainties of open Internet. So let me put another suggestion for Telos Z/IP One units.

Unlike APT which would use two streams sent over different Internet connections and then choosing the packets on the receiving end, Telos and Fraunhofer developed a technology to adapt to the varying network conditions. The Z/IP One codecs talk to each other, monitor the network connection between them and vary the bitrate, codec and buffering to always provide reliable, highest quality and lowest delay possible over the network/Internet connection used. For example, if the bandwidth drops, the units will scale down the bitrate and increase the buffering to compensate for the degradation in order to always keep audio going without break-ups (within the user set parameters). They also employ error correction and error concealment.

While Comrex units are also good, why I wouldn't use them for this application (STL) is because they are not 24-bit (at least I couldn't confirm in the specs and the manual) and both APT and Telos can do 24-bit. With 16-bit codecs you might have a need to have something (AGC) in front to protect it from being over driven and clipping, or suffer a higher noise floor if you leave enough headroom. With 24-bit codecs, there's enough dynamic range to go straight from the console to the codecs and not worry about the headroom, clipping or noise floor. And then have your processor at the transmitter site which is the best possible place for it!

Since with the Z/IP One you don't compromise on either of these points, that would be my choice.


Regards,
Goran Tomas

P.S. Last I've heard, Telos was also contemplating on adding a dual network path/redundancy feature to the Z/IP One, in addition to the adaptive technology mentioned above.

 

[richard.vanderveen]

Since with the Z/IP One you don't compromise on either of these points, that would be my choice.

Indeed, but there is another compromise I need to deal with: m o n e y ;D

Well Tom and Goran, I guess I'll see you both in Amsterdam... ;D

 

[comrex]

While Comrex units are also good, why I wouldn't use them for this application (STL) is because they are not 24-bit (at least I couldn't confirm in the specs and the manual) and both APT and Telos can do 24-bit.

Do you know what happens when you ass-ume?
BRIC-Link has 24 bit I/O. But I respectfully submit that someone who puts that spec over the ability to do the absolute best job over a varying Internet connection has his priorities a bit warped.